1. Field of the Invention
The present invention relates to a flat commutator including conductive carbon elements and more particularly to such a flat commutator for use in a motor for a fuel pump utilized in a fuel tank of an automobile or the like.
2. Description of the Prior Art
In general, fuel pumps have been used in automotive applications to supply liquid fuel contained in a fuel tank to the engine, and such fuel pumps are arranged in the fuel tanks.
On the other hand, due to a rising cost of normal fuel and an increased consideration for environmental contamination, there has been noticed a new fuel containing an oxygen compound, such as methyl alcohol and ethyl alcohol, etc. Therefore, when the fuel pump is used in the fuel tank containing such a fuel and if such a fuel pump includes a motor including a metallic commutator, it will corrode by the above mentioned alcohol contained in the fuel, so that the life of the motor is shortened. Under such a circumstance, a commutator which includes conductive carbon elements has been developed.
Such prior art commutators including the above mentioned conductive carbon elements are disclosed in U.S. Pat. Nos. 5,157,299 and 5,175,463 and in Japanese Utility Model Publication No. 2-53260.
Among these documents, U.S. Pat. No. 5,157,299 discloses a structure wherein carbon segments are connected to a metallic segment support through an adhesive layer of solder. U.S. Pat. No. 5,175,463 discloses a structure wherein segments are attached on a base through the intermediary of a first conductive layer of material such as nickel, copper, etc. and a second conductive layer of material such as gold, silver, etc. JUMP No. 2-53260 discloses a structure wherein a hub body is mechanically and electrically connected to carbon segments partially shaped to be of particular configuration.
In U.S. Pat. Nos. 5,157,299 and 5,175,463, however, there is no consideration of the strength of the commutator against a stress caused therein during its rotation, although suitable conductivity can be obtained in either case.
In addition, the commutator disclosed in JUMP No. 2-53260 is not always shaped to have a simple configuration, so that manufacture thereof is not easy.